Air-cooled engine



May 23, 1950 C. W. VAN RANST AIR-COOLED ENGINE s Shets-Sheet 1 FiledFeb. 5, 1945 Z s fi /H T Nd m A 6 M5 M, 0% I w mw 2 m y a M y 1950 c. w.VAN RANST 2,509,178

AIR-COOLED ENGINE Filed Feb. 5, 1945 3 Sheets-Sheet 2 5 M2 m5 m1 VINVENTOR. (2 2 172221 15 flf/dxz 774x 52.

BY E y 1950 c. w. VAN RANST 2,509,173

AIR-COOLED ENGINE 3 Sheets-Sheet 3 Filed Feb. 5, 1945 INVENTOR. (20822225 W/ Fairs Patented May 23, 1950 UNITED STATES PATENT OFFICEAIR-COLED ENGINE Cornelius W. Van Ranst, Dearborn, Mich. ApplicationFebruary 5, 1945, Serial N0. 576,277

4 Claims.

This invention relates to internal combustion engines and particularlyto those of the air cooled type, the principal object being theprovision of an engine of the type described so constructed and arrangedas to be more efficiently cooled than engines heretofore constructed.

Objects of the invention include the provision of a cylinder head of newand improved construction for air cooled internal combustion engines;the provision of a cylinder head for air cooled internal combustionengines so constructed and arranged as to substantially eliminate thedead air pockets found on the exterior surfaces of conventionally formedair cooled cylinder heads; the provision of a cylinder head of the typedescribed providing for a smooth and substantially unbroken flow of airover the external surfaces thereof; the provision of a cylinder head ofthe type described providing a materially increased finned area for thedissipation of heat as compared to conventional constructions in enginesof comparable sizes; the provision of a cylinder head of the typedescribed providing finned heat dissipating surfaces separate from thoseparts thereof called upon to withstand the explosion pressure of thecombustible mixture in the engine and so connected to the last-mentionedparts as to be capable of extracting a maximum amount of heat therefrom;the provision of a cylinder head for an air cooled engine so constructedand arranged as to provide a surface forming a part of the combustionchamber of the engine and increasing in its heat transmittingcharacteristics from the center of said combustion chamber toward theedges thereof and providing means connected to said edges forefficiently dissipating the heat flowing thereto; and the provision of aconstruction as last described in which the metal of the head isdisposed to accommodate a maximum efficiency in heat flow with a minimumof weight.

Other objects of the invention include the provision of an air cooledcylinder head for an internal combustion engine including a portionforming a part of the combustion chamber of the engine and marginalwalls integrally connected to such portion and extending outwardly awaytherefrom and suitably finned to dissipate the heat flowing thereto fromthe first-mentioned portion; the provision of a cylinder head as abovedescribed in which those portions thereof ex tending away from thatportion forming a part of the combustion chamber for the engine form atleast in part an enclosure for at least a part of the valve actuatingmechanism for the engine;

the provision of a cylinder head for an air cooled engine comprising amore or less cup or panshaped structure, the bottom of which serves toform a portion of the walls bounding the combustion chamber of theengine and the sides of which are finned to increase the transfer ofheat therefrom; the provision of a cylinder head of the constructionabove described in which a spark plug is located within the cylinderhead and the cylinder head is provided with a cover serving with thecylinder head to shield the spark plug and the electrical connectiontherefor; and the provision of a cylinder head construction as abovedescribed in which the exterior surfaces thereof provide a smooth andsubstantially unobstructed path for the flow of cooling air thereover.

Further objects of the invention include the provision of improved meansfor guiding the flow of air about an air cooled internal combustionengine; the provision of an air cooled internal combustion engine havingfins on the cylinder and head thereof together with means for effectinga distribution of air over said fins varying in volume in accordancewith the temperature of different portions thereof; and the provision ofa construction as above described including a housing surrounding thecylinder and cylinder head of the engine formed to admit airunrestrictedly along one side thereof, together with means forcontrolling the egress of the air from the opposite side thereof toprovide a flow varying over the length of the cylinder and head more orless proportionally to the variations in temperature over such length.

The above being among the objects of the present invention the sameconsists in certain novel features of construction and combinations ofparts to be hereinafter described with reference to the accompanyingdrawing, and then claimed, having the above and other objects in view.

In the accompanying drawings which illustrate a suitable embodiment ofthe present invention and in which like numerals refer to like partsthroughout the several different views,

Fig. 1 is a partially broken, partially sectioned end elevational viewof an engine embodying the principles of the present invention and takenas, for instance, on the line ll of Fig. 2;

Fig. 2 is a longitudinal sectional view of the engine shown in Fig. 1,taken as on the line 22 thereof;

Fig. 3 is a reduced horizontal sectional view taken through the cylinderhead of the engine 3 shown in the preceding views and as on the line 3-3of Fig. 2;

Fig. 4 is a fragmentary, end elevational view looking in the samedirection as the view shown in Fig. l but showing the shroud around thecylinder and cylinder head and the aperture therein for controlling theflow of air around the cylinder and the head; and

Fig. 5 is a more or less diagrammatic, vertical sectional view takendiagonally through a cylinder head of the character shown in thepreceding views, as, for instance, in the direction of the arrows 5-5 ofFig. 3, to more clearly bring out the principles of the presentinvention, a portion of a cylinder being shown connected thereto to aidin the explanation of said principles.

The present invention is, of course, adaptable for use in connectionwith air cooled engines of either the single or multiple cylinder type.the purpose of simplicity it is shown in the accompanying drawings inconnection with a single cylinder engine, as once the principles of thepresent invention are understood those skilled in the art will readilyrecognize the application of these principles to engines of themulticylinder type and be capable of applying such principles in thedesign thereof.

It is conventional practice in the formation of cylinder heads forinternal combustion. engines of the air cooled type to form the head asa cover for the cylinder and as part or all of the combustion chamberwhich is formed at the outer end of the cylinder, and to provide theports, rocker arm brackets or other mountings, spark plug bosses, andthe like on such surface and to fin all of these parts to withdraw heattherefrom. Air blown over such finned surfaces or otherwise flowing incontact therewith extracts the heat from the fins to provide a coolingeffect. Those skilled in the art recognize the fact that such ports orintake and exhaust passages, bosses, brackets and the like act to formpockets which resist the free flow of air through them and serve ineffect to provide dead air pockets from which it is extremely difficultto remove the desired amount of heat. The result is that certainportions of these cylinder heads become over-heated and cause hot spots,

resulting in pre-ignition of the combustible mixture and otherdeleterious efiects, and often establish limits beyond which theextension of other desirable features of the engine which mightotherwise increase the power and efficiency thereof is prohibited. Itis, therefore, the principal object of the present invention to providea cylind'er head construction for air cooled internal combustion engineswhich substantially eliminates such dead air pocketsmvhich provides foran increased flow of heat away from that portion of the cylinder headforming a part of the com.- bustion chamber for the engine, provides anincreased area of finned surface for the dissipation of such heat,andprovides for the smooth and unbroken flow of air about such finnedsurface whereby to enable a maximum amount of heat to be extractedtherefrom in a simple and efiicient manner. a

' Briefly, the advantages of the present invention are obtained bymaking the cylinder head of more or less cup or pan-like conformationwith the bottom wall thereof closing the end of the cylinder and formingat least a portion of the combustion chamber therefor, the sides of thecup or pan extending away from the cylinder and being exteriorly finned.Preferably such side walls are as smooth and of unbroken curvature aspossible,

For

except for the fins themselves, so that the air flowing about them andbetween the fin may flow without such abrupt changes in direction as areconducive to the formation of dead air pockets. In the interests ofconserving weight that portion of the head immediately over the cylinderis preferably made thinnest at its center where conveniently possiblewith increasing thickness towards its marginal edges in the plane of theend of the cylinder, thereb providing a path of increasing thicknessradiating outwardly from the center of the combustion chamber towardssuch margins to enable an increasing amount of heat to flow from thecenter to such edges. For the same reasons the side walls of the headare preferably of greatest thickness at their points of junction withthe bottom wall thereof and decrease in thickness in extending axiallyaway from the cylinder as in such case the amount of heat to betransmitted from the side walls decreases in this direction.

It has been found that the provision of a cylinder head of the typedescribed provides a direct and ready path. for the flow of heat fromthat portion of the head forming a part of the combustionv chamber forthe associated cylinders and provides a maximum amount Of finned areasfor the dissipation of such heat into the surrounding air, and thus evenin the absence of forced air circulation about the finned areas of thehead much more efficient cooling effect is had than is ordinarilycapable in conventional constructions. Inaddition because of thteformation of the head the valve stems and their cooperating springs, therocker arms, brackets, etc. and the spark plug are all located on theinterior of the head, the open end of which may be closed by a suitablecover thereby to completely enclose the same. This not only providesextremel efficient radio shielding for the spark plug but furtherprovidesan oil and moisture proof enclosure for the valve operatingmechanism in the head.

It will be appreciated that the present inventionmay be applied to aircooled engines regardless of the specific construction of the engineitself and it will, therefore, be appreciated that the particular engineshown in the accompanying. drawings and to which the present inventionis shown applied is shown in an illustrative and not in a limitingsense.

I Referring now to the accompanying drawings it will be noted that theengine there shown comprises a crankcase [0 having a cylinder l2 formedintegrally therewith. The crankcase i0 is shown as having one integralend wall and the opposite end open and normally closed by a removablecover member 14. It is assumed that in the particular case shown thecrankcase IE) and cylinder 12 is formed from a light metal such asaluminum or magnesium and the cylinder therefor is provided with a steelor other suitable liner such as It. In the particular construction shownthe crankcase I0 is illustrated as being provided with a web I 8 spaced:from its open face and formed toprovide a bearing 20 for the mainjournal 22 of the crankshaft 24, the latter of which is provided with apin 26 for receiving the big end of the connecting rod 28, the oppositeend of which is pivotally connected to a piston 3|] working in thecylinder HS in a conventional manner. The cover i=4 supports ananti-friction bearing 32 which forms a second bearing for the crankshaftspaced from the main journal 22 and outwardly of the bearing 32 asuitable or conventional grease seal 34 is provided in the cap l4.Axially outwardly of the seal 84 the crankshaft 24 has fixed thereto aflywheel 86 which mounts axially outwardly thereof and in concentricrelation with respect thereto a centrifugal fan element of aconventional type generally indicated at 38 and which will be referredto in greater detail presently.

The crankshaft 24 between the web I8 and the cover I4 has fixed theretoa gear 48. As brought out in Fig. 1 a second gear 42, of twice thediameter of the gear 48 and meshing with the gear 48, is mounted on acam shaft 44 rotatably supported .in the crankcase I8 in parallelismwith the crankshaft 24. The cam shaft 44 has formed thereon an exhaustcam46 and an inlet cam 48. Although forming no part of the presentinvention it may be noted that in radial alignment with the cam shaft 44and in alignment with each of the cams 46 and 48 the crankcase isprovided with a bore, one only of which is shown in Fig. 1, this borebeing indicated at 58 and as receiving therein a tappet in the form of acup 52, the closed end of which is adapted to ride on the correspondingcam 46 or 48. Within each tappet 52 is received a cup-like supportingmember 54 having a marginal flange portion at its open end whichrelatively closely fits the interior of the tappet 52 and which isperipherally relieved below such flange to provide a space 56 between itand the bore of the tappet 52. Below the flange of the support 54 thetappet 52 is provided with one or more holes 58therethrough which, whenthe tappet is adjacent its outer limit of reciprocation in the bore 58,becomes aligned with a groove 68 intersecting the bore 58 and to whichgroove 68 lubricant under pressure is constantly fed during operation ofthe engine. Such lubricant flows through the opening or openings 58downwardly into the chamber 56. The support 54 is centrally providedwith an axial opening 62 and the bottom of the support 54 is transversely grooved as at 64 to permit the fi'ow of lubricant from thechamber 56 into the opening 62. A hollow push rod 66 extends downwardlyinto the bottom of the support 54 and is provided with a partiallyspherical end surfaceseating in a complementarily shaped surface in thebottom of the support and is provided with an axial opening 68 inconstant open communication with the opening 62. The lubricant enteringthe chamber 56 from the groove 68 may thus flow through the groove 64and through the openings 62 and 68 into the hollow interior of the pushrod 66 and upwardly therethrough to the wearing surfaces of the rockerarms which are'mounted in the cylinder head and which will hereinafterbe described.

The cylinder I2 is, of course, provided with a multiplicity of radiallyoutwardly directed axially spaced cooling ribs or fins I8 thereon inaccordance with conventional practice and it will be understood that inplan view the exterior contour of these fins I8 may be square, round orany other suitable shape.

The upper end of the cylinder I6 is open and is normally closed by acylinder head constructed in accordance with the present invention. Asperhaps best brought out in Fig. 2 this cylinder head comprises a bottomwall 88 extending transversely across the open upper end of the cylinderI2 and secured thereto as by screws 82. The bottom wall 88 may be eitherround, square or of any other suitable contour in plan view but in asingle cylinder engine such as shown is preferably square and is soshown. The bottom wall 88 is marginally surrounded with upstanding sidewalls 84 integrally connected thereto, the bottom wall 88 and side walls84 thus providing in efiect a cup-like or pan-like'structure, the bottomof which closes the open upper end of the cylinder and forms a portionof the walls of the combustion chamber therefor. In the particular caseshown in Figs. 1 and 2 the lower wall 88 is provided over the bore ofthe cylinder l6 with a pocket 86 (see Fig. 2) the walls of which in thiscase form the major portion of the walls of the combustion chamber forthe cylinder I6.

The bottom wall 88 of the cylinder head is provided with a pair ofdownwardly opening ports 88 therein opening into the pocket 86 and isformed to provide a passage 98 connected with each of the ports 88 andextending outwardly through the side of the cylinder head, one extendingrearwardly as indicated in Fig. 2 and being connected as by a tube suchas 92 with a suitable carburetor or the like, and the other beingconnected as by a tube 92 either exhausting directly into the air orbeing connected to a suitablemuflier or the like. A valve stem guide 96is formed integrally with each passage 88 and with the bottom wall 88and is centrally apertured in alignment with the corresponding port 88for slidable reception of the stem 98 of a conventional poppet valve thehead of which is operatively associated with the corresponding port 88.A conventional coil spring I88 surrounds each valve stem 98 and ismaintained under compression between a shoulder formed on thecorresponding guide 96 and a spring retaining washer I82 mounted on theouter end of each valve stem 98 in a conventional manner. Upwardlyextending bracket means I84 are also formed integrally with the wall 88of the cylinder head and carry at their upper ends a shaft I86 uponwhicha pair of rocker arms I88 are pivotally supported, the outer ends of therocker arms lying in contact with the upper ends of the valve stems 98while the opposite ends thereof are provided with a transverselyextending axially adjustable socket head screw II8 which receives theupper ends of the push rods 66 therein.

The wall 88 is provided with a conventional threaded openingtherethrough leading into the pocket or combustion chamber 86 in which asparke plug I I2, shown in Fig. 1, is threaded with its operative endexposed in the pocket 86. The open upper end of the cylinder head isclosed by a cover I I4 suitably removably secured thereto. The cover andhead are provided with cooperating notches H6 and H8 at one side thereofin which an insulated plug I 28 is received. The plug I28 carries aconductor element 522 the inner end of which bears against the terminalat the outer end of the spark plug I2 and the outer end of which bearsagainsta terminal I24 of an electrical ignition cable I26 surrounded bya metal tube I28 socketed at its upper end in a lateral extension I38 ofthe cylinder head. This means of connecting the cable I26 with the sparkplug forms no part of the present invention and is illustrated merely asa means of providing an electrical connection for the spark plug withinthe cylinder head.

Reference may now be had to Fig. 5 which illustrates in a more or lessdiagrammatic manner the ideal form of the cylinder head when requiringno consideration of the inlet and exhaust ports and passages, rocker armbrackets, spark plug bosses, combustion chamber or the like-Disregarding these last-mentioned ele mentsthe lower wall 88 in suchcase might be providedwith a flat-lowersurface closing the open end ofthe cylinder I2 and in itsidealform and as illustrated in Fig. 5thebottom wall 80 would be a minimum thickness on the axial line of thecylinder 12 commensurate with the requirements of strength for this partof the head. The wall 80 would increase in thickness from its centertoward its lateral margin where it joins the side walls 84 and the sidewalls 84 would be of maximum thickness at their lower ends where theyjoin the wall 80 and extend upwardly in decreasing thickness to theupper marginal flange Hi where such is provided for reception of thecover I I4.

The reasons for this last described form of construction is as follows.It will be appreciated that that portion of the wall 80 overlying thebore of the cylinder l2 and forming a part of the combustion chamber forsuch cylinder is evenly exposed during operation to the same degree ofheat from the explosions of the combustible mixture occurring in thecombustion chamber. The heat in this particular case flows through thewall 80 radially outwardly to the marginal side walls 84 and, therefore,at least over the area of the bore of the cylinder I2 is required to beof increasing thickness from the center of the cylinder bore to theedges thereof to provide for, or to accommodate, the increased amount ofheat flow at the edges of the bore of the cylinder as compared to thecenter thereof. As the mass of the wall 88 provided for the flow of heatemanating from the center of the cylinder increases for each incrementof distance radially outwardly from the center of the cylinder an everincreasing path for the fiow of such heat is thus provided. The heatthus flowing to the periphery of the wall 80 is free to flow upwardlythrough the side walls 84 which present a maximum amount of mass forreception for such flow of heat, and the heat thus flows upwardlythrough the side walls 84. These side walls are provided with amultiplicity of integrally formed outwardly projecting cooling ribs orfins [42, preferably horizontally arranged in the particular embodimentshown and which act to thus dissipate the heat flowing through the sidewalls 86 to the air surrounding the head. This dissipation of heatthrough the fins I42 obviously decreases the amount of heat which isrequired to be dissipated in flowing toward the open end of the head sothat from a practical standpoint each increment of horizontalcross-sectional area of the head above the wall 80, that is of the sidewalls 84, may be successively reduced to correspond with the amount ofheat to be transmitted therethrough.

It will be understood, of course, that the tapering of the walls 80 and84 as particularly brought out in Fig. is theoretically the bestarrangement for obtaining a maximum heat flow with a minimum amount ofmetal and that from a practical standpoint, and particularly where themass of metal is more or less unimportant, this tapered formation maynot be of material importance from the standpoint of obtaining thedesired rapid dissipation of heat from the head. It will also beappreciated that, and as brought out particularly in Figs. 1 and 2, thenecessary provision of inlet and exhaust passages, rocker arm brackets,combustion chamber shapes or profiles, and the like may introduce manydif ficulties particularly in connection with providing the idealvariation of thickness in the bottom wall 89 of the head, butnevertheless where weight is of primary importance the variation in 8thickness of the bottomwall of the head to correspond with theconditions shown in Fig. 5 may at least be approached by careful design.Other requirements may also force modifications of the ideal conditions.For instance, and as brought out in Fig. 1, oil drain holes such as l32provided for drawing oil tending to accumulate in the cylinder head andreturning it through a tube such as I34 to the crankcase l0, and holessuch as I35 for passage of the push rods 65 through the cylinder headand for reception of the upper ends of the tubular housings I38 for thepush rods 86, may require modification of the disposition of the metalof the head to compensate for the heat flow path thus interrupted, or atleast varied, by the provision of such holes. These various departuresfrom the ideal conditions will be readily appreciated by those skilledin the art.

As previously mentioned the cross-sectional contour of the bottom walland side walls 84 of the cylinder head may be round, square or of anyother desired shape, that shown being square and being preferable inmany cases particularly in view of the fact that the valve mechanismsand spark plugs may require a considerable volume within the head toaccommodate the same. Likewise the contour of the peripheral edges ofthe fins H4 may be any shape desired regardless of the peripheral shapeof the wall 80 and the side walls 84 but in the case shown are squarethe same as the side walls 84.

. The important thing to note in connection with the above describedconstruction is that instead of only providing a bottom wall such as 8and providing cooling fins directly upon it and upon the inlet andexhaust passages 90, the valve guide bosses and the like as inconventional cylinder heads for air cooled engines, in which the amountof fin area is more or less restricted in any case and which inevitablyresults in the formation of so-called dead air pockets through which itis difficult to say the least to insure a satisfactory flow of coolingair, the construction provided by the present invention acts to draw theheat imparted to the wall 8!) to its marginal portions and thereconducts it up the side walls 84 whose exposed outer surfaces may bemade to present a materially greater area than would ever be prescut onthe upper surface of the wall 80, the passages 99, etc., and form theseside walls with smooth surfaces amply finned for the dissipation of heattherefrom. As a result cylinder heads constructed in accordance with thepresent invention have been found to be of materially greater eificiencyin the dissipation of heat from from a point to which they are limitedin engines having cylinder heads of conventional construction, thusresulting in an engine of increased power and efficiency forcorresponding sizes.

' Where cylinder heads of the present invention are applied tomulti-cylinder engines the design of the head may be varied tocorrespond depending upon whether the engine is of the individualcylinder type of the en bloc type. In other words where the engine is ofthe individual cylinder type, then each individual cylinder may beprovided with an individual head as in the particular case shown anddescribed, and, where the engine is of the en bloc type then a cylinderhead of corresponding length may be provided, the head in such casebeing provided with two side and two end walls suitably exteriorlyribbed in the same manner as the individual cylinder head heredescribed.

It has been found that cylinder heads constructed in accordance with thepresent invention will operate in most cases as eficiently withoutforced air cooling as conventional types of cylinder heads will operatewith forced air cooling. This, of course, is a result of the feature ofthe present invention providing rapid withdrawal of heat from the centerto the marginal portions of the head and dissipating this heat toextended surfaces having smooth exterior contours providing for theready and natural flow of air over them and ribbed or finned to increasethe heat dissipating qualities thereof. The use of forced air circulatedover the finned areas of the cylinder and head does, of course, serve togreatly increase the dissipation of heat from the cylinder head and isordinarily desirable, particularly in the case of high output engines,

In the last-mentioned connection and in accordance with another phase ofthe present invention means are provided for controlling the flow offorced circulation of air over the finned areas of the engine inaccordance with the needs of each portion. In other words it will beappreciated that the lower portions of the cylinder will not become ashot as the outer portions thereof and, therefore, do not require thevolume or flow of cooling air that the outer portions require.Additionally, the cylinder head usually requires the dissipation of amuch greater amount of heat than even the upper end of the cylinder and,accordingly, requires a correspondingly greater amount of flow ofcooling air than such upper end of the cylinder. In accordance with thisphase of the present invention the cooling air is fed to one side of thecylinder and the cylinder head and preferably in a manner permitting anequal flow to all portions in the length of the cylinder and cylinderhead, and the cylinder and cylinder head are shrouded for th flow of airtherearound and the egress of the air from the shroud is controlled toprovide for the desired volume of flow of air over the separate portionsof the length thereof. The means by which this is accomplished will nowbe explained in connection with this feature of the invention.

Referring now to Fig. 2 it will be noted that a sheet metal housing orshroud I56 is extended into surrounding relationship with respect to theflywheel 36 and fan 38. It is provided with an inlet opening I5I inaxial alignment with the flywheel 36 and fan 38 and with a cooperatingcollar I52 which projects axially a short distance into the fan 38. Theshroud I50 is generally spaced from the flywheel 36 and fan 38 and isprovided with a vertically extending portion I53 sealed at its loweredges about the crankcase and projecting upwardly around the cylinder I2and the cylinder head and is sealed at its upper end to the marginalflange I40 at the upper end of the head. As brought out in Fig. 2 theshroud I53 is spaced from the cylinder I2 and head on the flywheel sideof the engine so as to provide a vertical passage I54 through which theair drawn through the opening I5I and discharged by the fan 38interiorly of the shroud I56 may freely flow vertically for the fulllength of the cylinder and cylinder head. As best brought out in Fig. 3theshroud I53 relatively closely fits the fins l0 and I42 along thesidesand leithand face of the cylinder and cylinder head and, as brought outin Fig. 4, centrally of the leithand face of the enigne the shroud I53is provided with a vertically extending notch I56 therein, This notch isof a narrow V-like conformation, that is its narrowest dimensions areatthe bottom thereof adjacent the lower edge or" the shroud I53 andgradually increases in width toward the top. Around the exhaust passage60 which projects out therethrough the shroud I53 is spaced so as toprovide for the flow of air therearound.-

It will be appreciated that with the construction above described andwith the air from the fan 38 capable of flowing freely verticallythrough the passage ltd, the relative volume, or propor-,- tion of thetotal amount of air discharged by the fan 38, which flows between eachadjacent pair of fins 'Ill and I42 is controlled by the width of thenotch I56 at the discharge side of each suchpair. Thus a minimum amountof air may flow around the lower of the fins I6 and escape through thelower portion of the notch I56 while a greater amount of air may flowthrough the fins adjacent the upper end of the cylinder andescapethrough the corresponding portion of the notch;

I56, and an even greater amount of air may flow around the fins I42 ofthe cylinder head and escape out through the upper portion of the notchI56. Obviously the shape of the notch I56 may be varied to vary thevolume of flow of air at any particular point in the height of the notchto correspond with the amount of heat to be dissipatedfrom thecorresponding portion of the length of, the cylinder and cylinder headassembly. It will; be appreciated that by this method a simple andeifectlve means is provided for accurately and efficiently controllingthe how of the cooling air to obtain optimum cooling conditions for theengine as a whole.

Having thus described my invention, what I claim by Letters Patent is:

1. An air cooled cylinder head for an internal combustion enginecomprising a member adapted to be secured in sealing relation withrespect to the open end of an engine cylinder and having a singletransverse wall adapted to form a part of the combustion chambertherefor, inlet and exhaust passages formed integrally with said Walland opening therethrough, valves carried by said wall for controllingthe :rlow of fluid through said passages, a spam plug carried by saidwall within the margins thereof in operative relation with respect tothe combustion chamber adapted to be bounded thereby, a continuous sidewall iormed integrally with said transverse wall and extendingcompletely around the margins thereof and projecting away from that facethereof serving as a part of a combustion chamber, said side wallsencompassing said spark plug, valves and at least a portion of saidpassages, a plurality of generally spaced cooling tins formed integrallywith said walls on the outer surface thereof, and a closure removablysecured to the free margins of said side walls and sealing said valvesand spark plug within said side walls.

2. An air cooled cylinder head for an internal combustion engine havinga cylinder provided with an open end comprising, in combination, amember devoid of external lateral pockets comprising a single transversewall which is adapted to close the open end of said cylinder and to forma part of the combustion chamber therefor and side Walisrbrma integrallywith said transverse wall'exteiiding continuously around the marginsthereof and projecting perpendicularly to the planeof said transversewall, inlet and exhaust passages for said combustion chamber formedintegrally with said member and housed at least in part therein, valvesfor controlling said passages guided -in and carried by said member,rocker arms for operating said valves supported and housed within saidmember, a removable closure for the open end :of said member, and-aplurality of generally parallel and generally spaced integral coolingfins projecting -outwardly from *the odter surfaces of said side wallsof said member.

3. Anair cooledcylinder head for an internal combustion "engine having acylinder provided with an open end comprising 1 in combination, a memberhaving-a single transverse wall-which-is adapted to close the open end0f said cylinder and to form a part of the combustion chamber thereforand integral side walls projecting approximately perpendicularly to saidtransverse wall -continuously around the outer mar-gins thereof, inletand exhaust passages for s'aid combustion cham-ber iormed integrallywith said transverse walhand-housedat least -in-par-t therein, valvesfor controlling said passages guided ancl carried :by :said transverse'wall, rocker arms for operating said valves'supported and housed Within:said transverse wall, a -removableclosure for th-e open end' of saidmember, and-a plurality of generally parallel and generally spacedcooling fins projecting-outwardly from the outer surfaces of-said sidewalls and formed integrally therewith, said side walls increasing inthickness from the free :edges thereof toward their line --of junctionwith said transverse wall.

4. A cylinder head foran internal combustion 1 2' engine havingaiiyl'iiider rprovided w ith an open end eomprisi-ng, in combination, :aiinmber hav mg -a single transverse wall which is adapted to tiesecuredin see-1m relationship with respect to 'said open end of said cylinder-i'and to fol m a portionof the combustion chamber therefor andcontinuous side wa -11s .ro'rmed integrally with and projecting axiallyoutwardly from the peripheral niarlgihs "of 5 said transverse wan, -amultiplioitj of generally spaced :ooliii'g fins integrally joined toNumber Name 7 Date I "1247;81'9 Goodiifow Nov. 27, 191? 1, 13,35 'KtwoodJones, 1922 'isrtgseo Chilton Juneau, 1933 13812126 rharim Nov. 27, 1931 f1;9 e7; 1=*z'3 )Go'sslaut a1 "Apr, '9, 1935 205210}? jnbman "flu-325, 1 931; 2;,2'f2"5,,807 Towler Dec. 231, "1940 "22805660 N'wb'ofiibAprxzl, 1942 FoR' E-IGN EPAIPENTS Number Country new 291132 dre gnntam'Ji;1y 10,}19-19 357,362 'jGreat Britaih Oct. :1, -l9?;1 497;134 Greatefiain Dec. 13, 1938

